It is generally well known that to make particle diameter of a material smaller thereby increasing the specific surface area thereof not only enhances a reactivity of this material but also changes its properties relating to a handling characteristic such as bulk density. Among the methods for making particle diameter of a material smaller, a pulverizing process may be mentioned as one of the most basic unit processes thereof, and this process has been used for pulverization of minerals since early times, and for pulverization of an inorganic material such as calcium carbonate; and now it is used in very wide variety of fields.
Generally, a material having a crystalline structure has poor reactivity, so that its use has been difficult. In a certain pulverization process, a material can be made amorphous simultaneously with pulverization, whereby the reactivity thereof can be enhanced dramatically. As a result, various kinds of functional groups can be bonded by a chemical reaction to the amorphous material thereby obtained so that the value of this material may be enhanced dramatically.
In recent years, a biomass material is drawing increasing attention as the concern with the environmental problem is increasing; and a finely pulverized cellulose and an amorphous cellulose that are obtained by pulverizing a cellulose-containing raw material are being used as a raw material for a cellulose derivative such as a cellulose ether, and as an industrial raw material such as a cosmetic and a food stuff, a biomass material. For this, various kinds of pulverizers to be used for pulverization of the above-mentioned cellulose-containing raw materials have been proposed. For example, in Patent Document 1, it is disclosed that, after a wooden material is crushed, this crushed material is pulverized by a vibration mill provided with a upper first pulverizing trunk in which rods are accommodated as a pulverizing medium and with a lower second pulverizing trunk in which balls are accommodated as a pulverizing medium so that 90% or more by weight of the powders thereof can be pulverized to particle diameter of 100 μm or less by using this pulverization method. In the Patent Documents 2 and 3, a method to produce a cellulose which is made to amorphous by treating a cellulose-containing raw material having bulk density of 100 to 500 kg/m3 by a pulverizer such as a vibrating mill filled with balls or rods is disclosed.
In addition, in Patent Document 4, an apparatus to pulverize a wooden biomass wherein a plurality of thick plate discs having projections are inserted as the pulverizing medium into a cylindrical container whereby vibrating this cylindrical container up and down for pulverization is disclosed as a pulverizer to pulverize the particles further finely; and in Patent Document 5, similarly to the above, an apparatus to pulverize a wooden biomass wherein a rotating body having a plurality of projections and a hole in the axis direction in its central part is inserted as the pulverizing medium into a cylindrical container whereby revolving this cylindrical container for pulverization is disclosed as a pulverizer to pulverize the particles further finely.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-188833    Patent Document 2: Japanese Patent No. 4160108    Patent Document 3: Japanese Patent No. 4160109    Patent Document 4: Japanese Patent Laid-Open Publication No. 2008-93590    Patent Document 5: Japanese Patent Laid-Open Publication No. 2009-233542